i just installed my hotblast furnace. minimum clearance for the stovepipe is suppose to be 18 inches from any combustables. I am only 16" from combustables.The stovepipe goes thrue basement block wall and angles down sharply about 2' and then into the furnace. Only about 6" of the stovepipe is not 18" away from the floor joists, Can I use foil backed fiberglass ductwork for a shield. Will the insurance company deny coverage? Also the forced air ducts are suppose to be 6" from combustables. Can I use the same heatshielding for this? I cant comply w/ the 6" clearance because you would bang your head on the duct everytime you walk accross the basement. The wood furnace is located 20' away from the central propaine furnace. any help or advice would be appreciated.